1. Field of the Invention
The present invention relates to a sensing system using a plurality of sensor units, and a sensor unit used in the sensing system.
2. Related Background Art
X-ray sensing aiming at medical diagnosis is often done using a film screen system which combines intensifying screen and an X-ray radiographic film. According to this method, X-rays transmitted through an object contain the internal information of the object. This information is converted into visible light proportional to the intensity of the X-rays by the intensifying screen. The X-ray radiographic film is exposed to the light, and an X-ray image is formed on the film.
Recently, digital X-ray image sensing apparatuses are becoming popular in which X-rays are converted into visible light proportional to the intensity of the X-rays by a phosphor, the light is converted into an electrical signal using a photoelectric conversion element, and the signal is converted into digital data by an A/D conversion circuit.
In a sensing room for general X-ray image sensing, normally, an upright stand for a thoracic portion and a table for an abdominal portion or a leg are prepared to cope with all target sensing portions, using a cassette together. After sensed on the upright stand, the patient moves to the table for the next required sensing. At this time, the X-ray technician supports and positions the patient to prepare for appropriate sensing. After positioning, the X-ray technician goes back to the operation room to radiate X-rays. When a film screen system is used, the patient must wait after sensing until film development is ended. After confirming upon development that normal sensing has been performed, the next sensing operation starts. To the contrary, when a digital X-ray sensing apparatus is used, the X-ray technician positions the patient and then returns to the operation room to radiate X-rays. The resultant X-ray image can be confirmed on the display monitor in several seconds. Hence, the X-ray technician can immediately start the next sensing.
FIG. 1 shows a conventional scheme of general sensing using a digital X-ray sensing apparatus. An upright stand 9 having a sensor unit 3 is prepared in a sensing room and connected to a control section 7 in an operation room. An X-ray technician appropriately positions a patient 2 in front of the upright stand 9 first. The X-ray technician returns to the operation room and presses an X-ray radiation switch. X-rays are radiated from an X-ray generation apparatus 1 and transmitted through the patient 2. The X-rays with the internal information of the patient 2 become incident on the sensor unit 3. A solid-state image sensing apparatus 4 in the sensor unit 3 is constructed by bonding a phosphor 5 for converting X-rays into visible light proportional to the intensity of the X-rays to a photoelectric conversion apparatus 6 for converting the visible light into an electrical signal proportional to the light intensity. The X-ray image data converted into an electrical signal by the photoelectric conversion apparatus 6 is A/D-converted, transferred to the control section 7 as digital data, and displayed on display sections 8 and 10. Since several seconds are normally required from X-ray radiation to image display, the X-ray technician enters the sensing room to attend the patient 2 immediately after X-ray radiation and confirms the image on the display section 10.
In this prior art, since the apparatus has only the thoracic sensor unit, only the information of the thoracic portion of the patient is obtained. To obtain information except the thoracic information, e.g., abdominal information, an abdominal sensor unit must be prepared in the sensing room independently of the thoracic sensor unit.
When the apparatus has the thoracic and abdominal sensor units, the information of the thoracic portion of the patient is obtained first. Then, the patient moves to the abdominal sensor unit to obtain abdominal information.
At this time, the abdominal sensor unit must transit from the sleep state (low current state) in the nonuse mode to the ready state (normal current state). Normally, the photoelectric conversion apparatus 6 in the sensor unit requires several seconds for the transit period in which the ready state is set. For this reason, the next sensing cannot be started during this time. When the thoracic sensor unit and abdominal sensor unit are simultaneously set in the ready state, the problem of wait time can be avoided. However, the service life of the solid-state image sensing apparatus normally becomes short in inverse proportion to the ready-state time.